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LSR critical edge splitting fix for PR13756.

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llvm-svn: 164147
This commit is contained in:
Andrew Trick 2012-09-18 17:51:33 +00:00
parent 213f16cbf4
commit c987eb4cb3
2 changed files with 55 additions and 13 deletions
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24
lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -4464,17 +4464,21 @@ void LSRInstance::RewriteForPHI(PHINode *PN,
SplitLandingPadPredecessors(Parent, BB, "", "", P, NewBBs);
NewBB = NewBBs[0];
}
// If NewBB==NULL, then SplitCriticalEdge refused to split because all
// phi predecessors are identical. The simple thing to do is skip
// splitting in this case rather than complicate the API.
if (NewBB) {
// If PN is outside of the loop and BB is in the loop, we want to
// move the block to be immediately before the PHI block, not
// immediately after BB.
if (L->contains(BB) && !L->contains(PN))
NewBB->moveBefore(PN->getParent());
// If PN is outside of the loop and BB is in the loop, we want to
// move the block to be immediately before the PHI block, not
// immediately after BB.
if (L->contains(BB) && !L->contains(PN))
NewBB->moveBefore(PN->getParent());
// Splitting the edge can reduce the number of PHI entries we have.
e = PN->getNumIncomingValues();
BB = NewBB;
i = PN->getBasicBlockIndex(BB);
// Splitting the edge can reduce the number of PHI entries we have.
e = PN->getNumIncomingValues();
BB = NewBB;
i = PN->getBasicBlockIndex(BB);
}
}
}

44
test/Transforms/LoopStrengthReduce/2011-10-03-CritEdgeMerge.ll
View File

@ -1,15 +1,15 @@
; RUN: opt -loop-reduce -S < %s | FileCheck %s
;
; Test LSR's use of SplitCriticalEdge during phi rewriting.
; Verify that identical edges are merged. rdar://problem/6453893
target triple = "x86-apple-darwin"
; CHECK: @test
; Verify that identical edges are merged. rdar://problem/6453893
; CHECK: @test1
; CHECK: bb89:
; CHECK: phi i8* [ %lsr.iv.next1, %bbA.bb89_crit_edge ], [ %lsr.iv.next1, %bbB.bb89_crit_edge ]{{$}}
define i8* @test() {
define i8* @test1() {
entry:
br label %loop
@ -41,3 +41,41 @@ bb89:
exit:
ret i8* %tmp75phi
}
; Handle single-predecessor phis: PR13756
; CHECK: @test2
; CHECK: bb89:
; CHECK: phi i8* [ %lsr.iv.next1, %bbA ], [ %lsr.iv.next1, %bbA ], [ %lsr.iv.next1, %bbA ]{{$}}
define i8* @test2() {
entry:
br label %loop
loop:
%rec = phi i32 [ %next, %loop ], [ 0, %entry ]
%next = add i32 %rec, 1
%tmp75 = getelementptr i8* null, i32 %next
br i1 false, label %loop, label %loopexit
loopexit:
br i1 false, label %bbA, label %bbB
bbA:
switch i32 0, label %bb89 [
i32 47, label %bb89
i32 58, label %bb89
]
bbB:
switch i8 0, label %exit [
i8 47, label %exit
i8 58, label %exit
]
bb89:
%tmp75phi = phi i8* [ %tmp75, %bbA ], [ %tmp75, %bbA ], [ %tmp75, %bbA ]
br label %exit
exit:
%result = phi i8* [ %tmp75phi, %bb89 ], [ %tmp75, %bbB ], [ %tmp75, %bbB ], [ %tmp75, %bbB ]
ret i8* %result
}